• 제목/요약/키워드: aerodynamic test

검색결과 652건 처리시간 0.02초

Assessment of the aerodynamic and aerothermodynamic performance of a high-lift reentry vehicle

  • Pezzella, Giuseppe
    • Advances in aircraft and spacecraft science
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    • 제2권2호
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    • pp.109-124
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    • 2015
  • This paper deals with the aerodynamic and aerothermodynamic trade-off analysis of a hypersonic flying test bed. Such vehicle will have to be launched with an expendable launcher and shall re-enter the Earth atmosphere allowing to perform several experiments on critical re-entry phenomena. The demonstrator under study is a re-entry space glider characterized by a relatively simple vehicle architecture able to validate hypersonic aerothermodynamic design database and passenger experiments, including thermal shield and hot structures. A summary review of the aerodynamic characteristics of two flying test bed concepts, compliant with a phase-A design level, has been provided hereinafter. Several design results, based both on engineering approach and computational fluid dynamics, are reported and discussed in the paper.

말더듬에서 언제 보툴리늄독소주입술이 효과적인가에 관한 연구 (When the Botulinium Toxin Injection Is Effective in Stutters)

  • 안철민
    • 대한후두음성언어의학회지
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    • 제26권1호
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    • pp.46-50
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    • 2015
  • Background and Objectives:Laryngeal hyperkinetic movements of stuttering patients is similar to that of adductor spasmodic dysphonia. There has been studies on implementing botulinium toxin injections to treat stuttering. However, the opinions on the bouolinium toxin injection's effects on stuttering patients vary. In this study authors aim to figure out when the botulinium toxin injection improves stuttering patients. Materials and Methods:Stuttering patients who could receive botulinium toxin injection participated in this study. Age differences, gender differences, electroglottogrphic test, aerodynamic test in botulinium toxin injection treatment of stuttering were analyzed. Results:The botulinium toxin injection had statistically significant impact on patients who showed low mean air flow rate during aerodynamic study. Conclusion:The botulinium toxin injection could reduce stuttering of patients with low mean air flow rate in aerodynamic study.

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Wind tunnel blockage effects on aerodynamic behavior of bluff body

  • Choi, Chang-Koon;Kwon, Dae-Kun
    • Wind and Structures
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    • 제1권4호
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    • pp.351-364
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    • 1998
  • In wind tunnel experiments, the blockage effect is a very important factor which affects the test results significantly. A number of investigations into this problem, especially on the blockage correction of drag coefficient, have been carried out in the past. However, only a limited number of works have been reported on the wind tunnel blockage effect on wind-induced vibration although it is considered to be fairly important. This paper discusses the aerodynamic characteristics of the square model and square model with corner cut based on a series of the wind tunnel tests with various blockage ratios and angles of attack. From the test results, the aerodynamic behavior of square models with up to 10% blockage ratio are almost the same and square models with up to 10% blockage ratio can be tested as a group which behaves similarly.

요트세일의 풍동시험을 위한 공력 계측시스템 구축과 모형세일의 공력 계측 (A Construction of Aerodynamic Force Measurement System for Wind Tunnel Test of Yacht Sail and Aerodynamic Forces Measurement of Model Sail)

  • 김철희;최정규;김형태
    • 대한조선학회논문집
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    • 제48권5호
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    • pp.445-450
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    • 2011
  • In order to estimate a yacht sail performance, measuring system of aerodynamic forces acting on the yacht sail is constructed and experiments of flexible model sail are carried out at the medium-size subsonic wind tunnel of Chungnam National University. Experimental results for a flexible sail are compared with experimental and numerical results of fixed shape sail. In case of a fixed shape sail, lift and drag coefficients are rarely changed at all velocity conditions. However, those of the flexible sail are decreased as the incoming velocity is increased. These are understandably resulted from shape variations due to the flexible material. Therefore aero-elastic similarity should be more carefully considered in the model test rather than other similarities.

연축성 발성장애 환자의 음향학적 및 공기역학적 양상 (The Acoustic and Aerodynamic Aspects of Patients with Spasmodic Dysphonia)

  • 이주환;김인섭;고윤우;오종석;배정호;윤현철;최성희;최홍식
    • 대한후두음성언어의학회지
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    • 제11권1호
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    • pp.98-103
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    • 2000
  • Background and Objectives : The etiology and pathophysiology of spasmodic dysphonia is yet unknown. This study was performed to determine if any laryngeal aerodynamic parameter distinguish the voice of patient diagnosed as having adductor spasmodic dysphonia from individuals with normal voice production and to investigate the pathophysiology of spasmodic dysphonia. Materials and Methods : fifteen women diagnosed as having adductor spasmodic dysphonia and fifteen normal control women participitated in this study Maximum phonation time, mean air flow rate, subglottic pressure, vocal efficiency, Vfo, NHR, VTI, FTRI, ATRI, Jitter percent, Shimmer percent were obtained from the participants using 'MDVP(multi-dimensional voice program)' of CSL(Computerized Speech lab, Kay Elemetrics, Co., Model No. 4300), and 'maximum sustained phonation' and 'IPIPI test' of AP II(Aerophone II, Kay Elemetrics, Co., Model 6800). Results : T-test statistical analysis revealed statistically different values for vocal efficiency, Vfo, NHR, MPT, litter percent, Shimmer percent between the spasmodic dysphonia group and the control group. Conclusions : Spasmodic dysphonia affects the ability of the laryngeal mechanism to function effectively. Results from our study demonstrate that certain aerodynamic and acoustic parameters distinguish adductor spasmodic dysphonia from normal voice.

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Aerodynamic effects of subgrade-tunnel transition on high-speed railway by wind tunnel tests

  • Zhang, Jingyu;Zhang, Mingjin;Li, Yongle;Fang, Chen
    • Wind and Structures
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    • 제28권4호
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    • pp.203-213
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    • 2019
  • The topography and geomorphology are complex and changeable in western China, so the railway transition section is common. To investigate the aerodynamic effect of the subgrade-tunnel transition section, including a cutting-tunnel transition section, an embankment-tunnel transition section and two typical scenarios for rail infrastructures, is selected as research objects. In this paper, models of standard cutting, embankment and CRH2 high-speed train with the scale of 1:20 were established in wind tunnel tests. The wind speed profiles above the railway and the aerodynamic forces of the vehicles at different positions along the railway were measured by using Cobra probe and dynamometric balance respectively. The test results show: The influence range of cutting-tunnel transition section is larger than that of the embankment-tunnel transition section, and the maximum impact height exceeds 320mm (corresponding to 6.4m in full scale). The wind speed profile at the railway junction is greatly affected by the tunnel. Under the condition of the double track, the side force coefficient on the leeward side is negative. For embankment-tunnel transition section, the lift force coefficient of the vehicle is positive which is unsafe for operation when the vehicle is at the railway line junction.

Aerodynamic parameters selection and windbreak mechanism of wind barrier for high-speed railway bridge

  • Yujing Wang;Weiwei Guo;He Xia;Qinghai Guan;Shaoqin Wang
    • Wind and Structures
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    • 제38권6호
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    • pp.411-425
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    • 2024
  • To investigate the optimal aerodynamic parameters of wind barriers for the T-beam of high-speed railway (HSR) bridge and the wind field of the wind barrier-train-bridge system, the three-component forces of the system and the wind pressure on the vehicle surface were tested and analyzed through the sectional model wind test. The effects of wind velocity, with/without wind barrier, the height of wind barrier, and the air permeability of the wind barrier on the aerodynamic characteristics of the train-bridge system are discussed. Additionally, a CFD numerical model is constructed to evaluate the wind environment of the bridge surface with/without the wind barrier, and the impact of wind barrier on the running safety of vehicles are analyzed. Comprehensively considering the running safety of the train and the wind-resistant stability of the bridge, it is more appropriate to set the wind barrier height H as 3.5 m and the porosity 𝛽 as 30% respectively.

Experimental and numerical study on aerodynamic characteristics of suspended monorail trains passing each other under crosswinds

  • Yulong Bao;Wanming Zhai;Chengbiao Cai;Shengyang Zhu;Yongle Li
    • Wind and Structures
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    • 제37권5호
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    • pp.361-373
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    • 2023
  • Suspended monorail trains (SMTs) are sensitive to crosswinds, and instantaneous aerodynamic characteristics of two SMTs passing each other under crosswinds are particularly complicated. In this study, a pressure measurement test is carried out on stationary train-bridge models arranged in several critical positions. In addition, a validated moving CFD model is developed with the dynamic and sliding mesh method to explore the realistic train movement effects. The time-varying aerodynamic forces and surface pressure distribution on, as well as the flow field around running trains and bridges during trains passing each other, are computed in detail to illustrate the shielding effect of the upstream train. The results reveal that when two trains begin to pass each other, the side force coefficient of the downstream train reduces significantly to negative values due to the wind shielding effect of the upstream train. The moving model successfully captures that airflow is separated on the middle line of the head car for the suspended monorail train, and the surrounding bluff double-beams can significantly affect the flow structures around the train. The wind shielding effect of the upstream train on the downstream train will weaken as the relative yaw angle decreases.

능동 난류 생성을 통한 장대 교량의 공력 특성 비교 (Aerodynamic Characteristics of Long-Span Bridges under Actively Generated Turbulences)

  • 이승호;권순덕
    • 대한토목학회논문집
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    • 제31권5A호
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    • pp.341-349
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    • 2011
  • 본 연구에서는 다양한 풍동실험을 통하여 기류 조건에 따른 트윈박스 거더 교량의 공기역학적 특성을 파악하는데 그 목적이 있다. 이를 위하여 자연적인 난류를 생성할 수 있는 능동 난류 발생장치를 개발하였고 검증하였다. 그리고 능동 난류 및 격자 난류 조건하에서 정적공기력, 비정상공기력 그리고 버페팅 응답 측정 실험을 수행하였다. 풍동실험 결과를 보면, 난류 적분길이는 교량의 정적공기력과 $A_1^*$를 제외한 플러터계수에는 영향을 주지 않는 것으로 나타났다. 그리고 난류 강도는 비정상공기력에 일부 영향을 미치고, 난류 적분길이 또한 일부 수직 방향 성분에 영향을 주는 것으로 나타났다.

Effect of beam slope on the static aerodynamic response of edge-girder bridge-deck

  • Lee, Hoyeop;Moon, Jiho;Chun, Nakhyun;Lee, Hak-eun
    • Wind and Structures
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    • 제25권2호
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    • pp.157-176
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    • 2017
  • 2-edge box girder bridges have been widely used in civil engineering practice. However, these bridges show weakness in aerodynamic stability. To overcome this weakness, additional attachments, such as fairing and flap, are usually used. These additional attachments can increase the cost and decrease the constructability. Some previous researchers suggested an aerodynamically stabilized 2-edge box girder section, giving a slope to the edge box instead of installing additional attachments. However, their studies are limited to only dynamic stability, even though static aerodynamic coefficients are as important as dynamic stability. In this study, focus was given to the evaluation of static aerodynamic response for a stabilized 2-edge box girder section. For this, the slopes of the edge box were varied from $0^{\circ}$ to $17^{\circ}$ and static coefficients were obtained through a series of wind tunnel tests. The results were then compared with those from computational fluid dynamics (CFD) analysis. From the results, it was found that the drag coefficients generally decreased with the increasing box slope angle, except for the specific box slope range. This range of box slope varied depending on the B/H ratio, and this should be avoided for the practical design of such a bridge, since it results in poor static aerodynamic response.